﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace GraphTools
{
    public sealed class Haversine
    {
        /// <summary>
        /// The distance type to return the results in.
        /// </summary>
        public enum DistanceType { Miles, Kilometers };

        /// <summary>
        /// Returns the distance in miles or kilometers of any two
        /// latitude / longitude points.
        /// </summary>
        /// <param name=”pos1″></param>
        /// <param name=”pos2″></param>
        /// <param name=”type”></param>
        /// <returns></returns>
        public static double Distance(Node pos1, Node pos2,DistanceType type)
        {
            double R = (type == DistanceType.Miles) ? 3960 : 6371;
 
            double dLat = toRadian(pos2.Latitude - pos1.Latitude);
            double dLon = toRadian(pos2.Longitude - pos1.Longitude);
 
            double a = Math.Sin(dLat / 2) * Math.Sin(dLat / 2) +
                Math.Cos(toRadian(pos1.Latitude)) *Math.Cos(toRadian(pos2.Latitude)) *
                Math.Sin(dLon / 2) * Math.Sin(dLon / 2);
            double c = 2 * Math.Asin(Math.Min(1, Math.Sqrt(a)));
            double d = R * c;
 
            return d;
        }
 
        /// <summary>
        /// Convert to Radians.
        /// </summary>
        /// <param name=”val”></param>
        /// <returns></returns>
        private static double toRadian(double val)
        {
            return (Math.PI / 180) * val;
        }
    }
}
